普通状态下的文字属性

 // 普通状态下的文字属性
NSMutableDictionary *normalAttrs = [NSMutableDictionary dictionaryWithCapacity:0];
 // 设置字体
normalAttrs[NSFontAttributeName] = [UIFont systemFontOfSize:14];
 // 设置文字颜色
 normalAttrs[NSForegroundColorAttributeName] = [UIColor grayColor];

// 设置
[vc.tabBarItem setTitleTextAttributes:normalAttrs forState:UIControlStateNormal];

选中状态下的文字属性

// 选中状态下的文字属性
NSMutableDictionary *selectedAttrs = [NSMutableDictionary dictionaryWithCapacity:0];

selectedAttrs[NSForegroundColorAttributeName] = [UIColor darkGrayColor];

// 设置
[vc.tabBarItem setTitleTextAttributes:selectedAttrs forState:UIControlStateSelected];

添加子控制器

/**
 * 添加所有的子控制器
 */
- (void)setupChildVcs
{
    [self setupChildVc:[[XMGEssenceViewController alloc] init] title:@"精华" image:@"tabBar_essence_icon" selectedImage:@"tabBar_essence_click_icon"];
    
    [self setupChildVc:[[XMGNewViewController alloc] init] title:@"新帖" image:@"tabBar_new_icon" selectedImage:@"tabBar_new_click_icon"];
    
    [self setupChildVc:[[XMGFriendTrendsViewController alloc] init] title:@"关注" image:@"tabBar_friendTrends_icon" selectedImage:@"tabBar_friendTrends_click_icon"];
    
    [self setupChildVc:[[XMGMeViewController alloc] initWithStyle:UITableViewStyleGrouped] title:@"我" image:@"tabBar_me_icon" selectedImage:@"tabBar_me_click_icon"];
}

/**
 * 添加一个子控制器
 * @param title 文字
 * @param image 图片
 * @param selectedImage 选中时的图片
 */
- (void)setupChildVc:(UIViewController *)vc title:(NSString *)title image:(NSString *)image selectedImage:(NSString *)selectedImage
{
    // 包装一个导航控制器
    XMGNavigationController *nav = [[XMGNavigationController alloc] initWithRootViewController:vc];
    [self addChildViewController:nav];
    
    // 设置子控制器的tabBarItem
    nav.tabBarItem.title = title;
    nav.tabBarItem.image = [UIImage imageNamed:image];
    nav.tabBarItem.selectedImage = [UIImage imageNamed:selectedImage];
}

/**
 * 设置item属性
 */
- (void)setupItem
{
    // UIControlStateNormal状态下的文字属性
    NSMutableDictionary *normalAttrs = [NSMutableDictionary dictionary];
    // 文字颜色
    normalAttrs[NSForegroundColorAttributeName] = [UIColor grayColor];
    // 文字大小
    normalAttrs[NSFontAttributeName] = [UIFont systemFontOfSize:12];
    
    // UIControlStateSelected状态下的文字属性
    NSMutableDictionary *selectedAttrs = [NSMutableDictionary dictionary];
    // 文字颜色
    selectedAttrs[NSForegroundColorAttributeName] = [UIColor darkGrayColor];
    
    // 统一给所有的UITabBarItem设置文字属性
    // 只有后面带有UI_APPEARANCE_SELECTOR的属性或方法, 才可以通过appearance对象来统一设置
    UITabBarItem *item = [UITabBarItem appearance];
    [item setTitleTextAttributes:normalAttrs forState:UIControlStateNormal];
    [item setTitleTextAttributes:selectedAttrs forState:UIControlStateSelected];
}

自定义tabbaritem

#import "TTTabBar.h"
#import "TTPublishViewController.h"

@interface XMGTabBar()
/** 发布按钮 */
@property (nonatomic, weak) UIButton *publishButton;
@end

@implementation XMGTabBar

- (instancetype)initWithFrame:(CGRect)frame
{
    if (self = [super initWithFrame:frame]) {
        // 设置背景图片
        self.backgroundImage = [UIImage imageNamed:@"tabbar-light"];
        
        // 添加发布按钮
        UIButton *publishButton = [UIButton buttonWithType:UIButtonTypeCustom];
        [publishButton setBackgroundImage:[UIImage imageNamed:@"tabBar_publish_icon"] forState:UIControlStateNormal];
        [publishButton setBackgroundImage:[UIImage imageNamed:@"tabBar_publish_click_icon"] forState:UIControlStateHighlighted];
        [publishButton sizeToFit];
        [publishButton addTarget:self action:@selector(publishClick) forControlEvents:UIControlEventTouchUpInside];
        [self addSubview:publishButton];
        self.publishButton = publishButton;
    }
    return self;
}

- (void)publishClick
{
    TTPublishViewController *publish = [[TTPublishViewController alloc] init];
    [self.window.rootViewController presentViewController:publish animated:NO completion:nil];
}

/**
 * 布局子控件
 */
- (void)layoutSubviews
{
    [super layoutSubviews];
    
    // tabBar的尺寸
    CGFloat width = self.width;
    CGFloat height = self.height;
    
    // 设置发布按钮的位置
    self.publishButton.center = CGPointMake(width * 0.5, height * 0.5);
    
    // 按钮索引
    int index = 0;
    
    // 按钮的尺寸
    CGFloat tabBarButtonW = width / 5;
    CGFloat tabBarButtonH = height;
    CGFloat tabBarButtonY = 0;
    
    // 设置4个TabBarButton的frame
    for (UIView *tabBarButton in self.subviews) {
        if (![NSStringFromClass(tabBarButton.class) isEqualToString:@"UITabBarButton"]) continue;
        
        // 计算按钮的X值
        CGFloat tabBarButtonX = index * tabBarButtonW;
        if (index >= 2) { // 给后面2个button增加一个宽度的X值
            tabBarButtonX += tabBarButtonW;
        }
        
        // 设置按钮的frame
        tabBarButton.frame = CGRectMake(tabBarButtonX, tabBarButtonY, tabBarButtonW, tabBarButtonH);
        
        // 增加索引
        index++;
    }
}

@end

在自定义的TabBarController中

/**
 * 处理TabBar
 */
- (void)setupTabBar
{
// 因为tabBar是只读属性，通过KVC进行设置
    [self setValue:[[TTTabBar alloc] init] forKeyPath:@"tabBar"];
}